a) Field of the invention
The present invention relates to an image stabilizing optical system, and more specifically to an image stabilizing optical system which is suited for correcting blur of images produced by vibrations, etc. of photographic cameras, video cameras and so on.
b) Description of the prior art:
Images of objects which are photographed from travelling vehicles and flying aircrafts are blurred due to vibrations transmitted to photographic systems. As means for preventing such hindrance, there have hitherto been proposed various image stabilizing optical systems utilizing plane parallel plates and wedge-shaped prisms.
FIG. 1 illustrates an example of the conventional image stabilizing optical systems which comprises a plane parallel plate 2 arranged on the side of an image surface 3 of a master lens 1 and functions to correct blur of an image formed on the image surface 3 by inclining the plane parallel plate 2 in conjunction with degree of vibration of the image.
FIG. 2 shows another example of the conventional image stabilizing optical systems which comprises a prism 4 having a variable vertical angle which is composed of two types of transparent elastic members 4a and 4b arranged on the object side of the master lens 1, and functions to correct blur of an image formed on the image surface 3 by varying the vertical angle of the prism 4 with two actuators 5 in conjunction with degree of vibration of a photographic system as a whole.
FIG. 3A and FIG. 3B show a third conventional example disclosed by Japanese Patent Preliminary Publication No. Hei 1-140119 which comprises a pair of wedge-shaped prisms 6a and 6b arranged on the side of the image surface of the master lens 1, and functions to correct blur of an image formed on the image surface 3 by moving the wedge-shaped prisms 6a and 6b along the optical axis so as to vary the interval therebetween in conjunction with degree of vibration of the image.
However, when the exit pupil of the master lens 1 is located relatively near the image surface 3 in the image stabilizing optical system illustrated in FIG. 1 the plane parallel plate 2 corrects the image position at degrees different between the central portion and the marginal portion of the image surface 3, whereby the image stabilizing optical system has a defect that it produces new blur on the marginal portion after the blur is corrected at the central portion. Further, the image stabilizing optical system shown in FIG. 2 has a defect that it requires a strong force to control the vertical angle of the prism and must use large actuators for this purpose, thereby enlarging the photographic system to be used therewith and making it difficult to obtain quick response of the photographic system. Furthermore, the image stabilizing optical system shown in FIG. 3A and FIG. 3B cannot practically correct blur in the direction perpendicular to the paper surface without using an additional pair of prisms which are similar to the prisms 6 and arranged perpendicularly thereto, and requires two pairs of wedge-shaped prisms arranged on the image surface 3 of the master lens 1. Accordingly, this image stabilizing optical system has defects that it enlarges the photographic system, that it requires two actuators or complicated control therefor, and that the master lens must have a long back focal length, thereby making it difficult to design a master lens having favorably corrected aberrations.